Semiconductor modules for switching control of current and made up of IGBTs or MOS-FETs are main components of power conversion devices such as inverters and chargers. Power conversion devices are required to deliver ever higher output to match the ongoing progress in electric-powered vehicles, and current capacity of semiconductor modules shows a trend towards an increase.
Concomitantly with the evolution of semiconductor elements of SiC or the like, such elements can now operate in high-temperature environments at around 200° C., and structural reliability in thermal cycling has become much stricter than it was conventionally. Semiconductor modules are therefore required to afford increased current capacity from higher output, while also securing reliability in terms of being capable of operating normally over long periods of time in a high-temperature environment.
In order to increase current capacity it is essential to reduce the electric resistance value of a current-carrying member. In order to secure reliability in environments from low temperature to high temperature, moreover it is essential to reduce cold thermal stress at joints of constituent members inside a semiconductor module, and to reduce residual stress at these joints.
Conventional semiconductor modules include instances where a conductive member is directly joined to an electrode of a semiconductor element, in order to increase current capacity (for instance, PTL 1).